In certain industrial applications there is a need for alloys which possess high rupture strength, high corrosion resistance, good oxidation resistance, low creep rates and high elongation to failure at elevated temperatures. Among such applications is the glass fiber industry where filaments are produced by passing molten glass material through the foraminous walls of a chamber which is adapted for rotation at high speeds. This chamber is generally known in the art as a spinner and the filaments are emitted through the fiberizing orifices in the walls due to the centrifugal action of the rotating spinner. Such spinners are typically operated at temperatures on the order of about 2050.degree. F. and rotational speeds on the order of 2050 rpm.
It is advantageous from a production cost standpoint for the rotation speed of the spinner to be as high as possible so as to increase the rate at which filaments are emitted through the fiberizing orifices. However, high spinner rotational speeds result in reduction in spinner life due to the limited strength of the alloys. Additionally, it is necessary to have an alloy which has a low creep rate. If a suitable alloy were available, additional cost savings could be realized by fiberizing low cost batch formulations, such as higher viscosity glasses than that normally used to produce fibers for glass insulation (wool glass).
What is needed in the art is an alloy which has good glass corrosion and erosion resistance and one which has a maximized stress rupture life and a minimized creep rate, with acceptable elongation, under the conditions of use in the formation of glass fibers. Additionally there is a need for such alloys to be substantially free of such expensive constituents as yttrium, hafnium and dysprosium.
U.S. Pat. Nos. 3,933,484, 4,497,771, 4,668,265 and 4,668,266 disclose cobalt based alloys having many beneficial properties allowing them to be used as spinners in the formation and attenuation of glass fibers. Unfortunately, however, these patents do not describe, teach or suggest any techniques, formulations or relationships as to how one is to obtain an alloy having maximum values for properties which need to be high and minimum values for properties that need to be low. That is, there is nothing in these references suggesting a result effective variable for maximizing the stress rupture life while simultaneously minimizing the creep rate for a prescribed class of cobalt based alloys.